To the legacy of the SMART system belongs the so-called SMART notation, a mnemonic scheme for denoting tf-idf weighting variants in the vector space model. The mnemonic for representing a combination of weights takes the form ddd.qqq, where the first three letters represents the term weighting of the document vector and the second three letters represents the term weighting for the query vector. The letter representation for a term, <math> t </math>, and document, <math> d </math>, is as follows:[1]